1. Field of Invention
This invention relates to an improved medium for the selective and differential culture of Campylobacter species, especially C. jejuni and C. coli.
2. Description of the Prior Art
Campylobacter jejuni, C. coli and C. laridis are known to cause an estimated 2.2 million cases of foodborne gastroenteritis per year in the United States alone (Tauxe et al., 1987, Am. J. Public Health, 77:1219-1221). The vast majority of these cases are associated with the consumption of improperly prepared poultry or foods and hands cross-contaminated by raw poultry. Although the origin of this disease in humans is primarily linked to poultry, the food microbiology and poultry communities have been slow in directing substantive attention toward the organism. In part, this has been due to the unique physiological requirements of these organisms, impairing their culture and identification from foods and clinical specimens.
A variety of enrichment and culture media have been proposed for the isolation of Campylobacter species Park et al, Campylobacter, In: Compendium of Methods for the Microbiological Examination of Foods, second edit., M. L. Speck (ed.), Am. Pub. Hlth. Assoc., Washington, D.C., 1984, p. 386-404, the contents of which are incorporated by reference herein!. Because Campylobacter can be overgrown by other organisms present in sect sources, the use of selective media, incorporating antibiotics and/or antimicrobial agents, is essential for their culture. Ideally, any culture medium selected should also be differential, allowing the characterization of the Campylobacter by distinctive colonial appearances in culture.
Butzler developed a selective medium for C. jejuni containing a nutrient agar base, blood, and five selective agents, cycloheximide, cefazolin, bacitracin, colistin sulfate and novobiocin, as described by Smibert Canpylobaceer, In: Bergey's Manual of Systematic Bacteriology, Vol. 1, Krieg and Holt (ed.), Williams and Wilkins, Baltimore, Md., 1984, pages 111-115, the contents of which are incorporated by reference herein!. Other selective media that have been developed include: Preston medium (Hut hinson and Bolton, J. Clin. Pathol., 1983, 36:1350-1352) containing nutrient broth, agar, lysed horse blood, cyclohemimide, polymyxin sulphate, trimethoprim lactate and rifampicin; Skirrow's medium (Skirrow, Br. Med. J., 1977, ii:9-11) containing a nutrient agar base, lysed horse blood, vancomycin, polymyxin and trimethoprim; and Camipy-BAP (Blaser et al., 1979, Ann. Intern. Med., 91:179-185) containing brucella agar, sheep erythrocytes, vanoocycin, trimethoprim, polymyxin B, cephalothin, and amphotericin B. While all of these media offer some selectivity, the degree of this selectivity has been limited, and the growth of some strains of Campylobacter may be inhibited as well.
One agar medium in particular, CCDA, has gained prominence for the isolation of Campylobacter. Early formulations of CCDA (Hutchinson and Bolton, 1983, J. Clin. Pathol., 36:1350-1352) contained nutrient broth, agar, charcoal, casein hydrolysates, ferrous sulfate, sodium pyruvate and, as selective agents, sodium deoxyoholate and cephazolin. In later formulations the cephazolin was replaced with cefoperazone for improved selectivity (Hutchinson and Bolton, 1984, J. Clin. Pathol., 37:956-957). However, colonies of Campylobacter grown on CCDA have been difficult to differentiate from colonies of other containing microorganisms